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Question: “With the ever increasing electric car fires, how are our local fire departments going to respond and how can they put out those fires? How dangerous are the toxic fumes to firefighters and the environment?”
MANSFIELD — The good news is electric-powered vehicles have the least risk of catching fire according to data from the National Transportation Safety Board.
Battery-electric vehicles are only .03% likely to ignite, compared to 1.5% for gas-powered vehicles and 3.4% for hybrid vehicles.
The bad news is — when an EV does catch fire, it’s a far bigger problem than a gas-powered car.
Mansfield Fire Dept. Brian Danals said new equipment isn’t necessarily needed to battle electric vehicle fires.
The issue is one of water — lots of water — according to Danals, who is in charge of training at the MFD.
With traditional vehicle fires, the challenge is much simpler. Firefighters arrive on scene, knock out the fire, let it cool and then have it towed away.
But a fire in an EV, powered by its large lithium-ion battery, presents a greater challenge in terms of water supply.
Danals said the MFD has yet to encounter an EV blaze, but said the department is developing a response plan.
“Just as we do with a regular car fire, we will have structural fire gear on with air tanks so we are protected,” said Danals, who has been with the Mansfield Fire Department for 34 years. “We will try to attack with a hand line.”
“We want to put a lot of water on it and protect exposures while the (EV) fire burns itself out,” he said.
The problem, according to Danals, is the department’s fire engines only carry 750 gallons of water, a supply usually adequate to squelch a traditional car fire.
But an EV fire may take tens of thousands of gallons due to the issues presented by the vehicle’s battery.
According to an article at www.firerescue1.com, a high-voltage battery is made up of many cells packed tightly together inside a watertight, fire-resistant box.
“When a single cell fails, it is essentially a small explosive that produces a tremendous amount of gas and heat (1,200 degrees F) in tenths of a second. The failure is an exothermic chemical reaction that does not require oxygen from the atmosphere to sustain itself. The heat released from each individual cell is transferred to the neighboring cells, which causes them to fail as well,” according to the article, written by Troy (Mich.) fire Capt. Patrick Durham.
“Once a battery cell fails, it is impossible to extinguish the failed cell as the chemical reaction inside the cell happens far too quickly. The only way to stop a thermal runaway is by directly cooling the cells involved to ensure that the failed cell does not cause the cells around it to also fail,” according to the article.
According to an article published by a Johnstown, Penn., TV station, a recent EV blaze involving a Tesla took 12,000 gallons of water and two hours to finally put out the flames.
Danals said Mansfield firefighters would rely on nearby hydrants if available. If not, the response would include sending additional resources to the blaze.
It’s not an issue Danals contemplated when he began his firefighting efforts more than three decades ago.
“In the fire services, you are always learning,” he said with a laugh.
Durham wrote there is no simple solution or tool to stop a thermal runaway in an EV’s high-voltage battery.
“Directly cooling the battery cells is the best method, however the manufacturers do not give first responders direct access to the inside of the battery box. Trying to cool the battery cells from the outside will only extend a crew’s time on scene,” he wrote.
“If the battery box is intact and there are no exposures, the best solution is to simply wait for the battery to burn itself out, then extinguish the remaining class A fire.
“While this strategy is not ideal – and not one favored by aggressive, proactive and eager firefighters – it’s really the best approach. It should only take an hour for the battery to burn itself out. The alternative will be to continually dump water on the vehicle for 6 to 8 hours,” Durham wrote.
